1. Field of the Invention
The present invention relates to contact lens cleaning methods and compositions. In particular, this invention relates to the use of carbon dioxide and carbonic acid to clean contact lenses.
2. Description of Related Art
Numerous contact lens care cleaning compositions are known. Contact lens cleaning products typically contain polymeric beads, enzymes, surfactants, or some combination thereof, as cleansing ingredients. Repeated use of cleaning compositions containing polymeric beads, such as Teflon or silicon dioxide beads, can damage the surface of contact lenses. Additionally, if all polymeric beads are not rinsed from the lens before inserting the lens in the eye, any residual beads may irritate the eye.
Enzymatic cleaners are popular cleansing agents for contact lenses, particularly for their ability to remove protein deposits. Raw material control for both enzymes and polymeric beads is often difficult. As in the case of polymeric beads, enzymes can be irritating to the eye if not thoroughly rinsed from the contact lens before it is inserted. Enzyme-containing cleaning products also suffer the disadvantage that they are generally incapable of being sterilized with heat, as the high temperatures required for sterilization can chemically degrade enzymes.
Surfactants are typically ineffective for cleaning protein deposits and are also generally irritating to the eye.
JP 01179123A (890717) discloses contact lens cleaning compositions containing percarbonate and an anionic or nonionic surfactant. The reaction of percarbonate with water generates oxygen bubbles. The reference attributes the cleaning to the mechanical cleaning action of the bubbles and the chemical cleaning action of the surfactant.
EP 93784A (831116) discloses enzymatic cleaning compositions for contact lenses. The cleaning compositions are comprised of an effervescent tablet containing trypsin, alpha-amylase, lipase, citric acid, sodium bicarbonate, calcium acetate and EDTA.
JP 88059123B (881117) discloses a foaming, contact lens cleaning tablet composition containing sodium bicarbonate, an organic or inorganic acid (or salt thereof, an enzyme, and a surfactant. When combined with clean water, the reference tablet foams, removing stains from the surface of contact lenses by the physical action of the foam. After foaming, remaining stains are removed by the enzyme and the surfactant.
Therefore, it is highly desirable to have lens care cleaning compositions which are capable of effectively cleaning proteinaceous and nonproteinaceous deposits from lenses, but which do not require the presence of polymeric beads, enzymes or cleansing amounts of surfactants.